Head lice infestations (“pediculosis capititis”) are a worldwide endemic problem. Although accurate data on the yearly, worldwide number of lice infestations is not available, the U.S. Centers for Disease Control and Prevention estimates that 6 to 12 million infestations occur each year in the United States alone among children 3 to 11 years of age.
FIG. 1A depicts a mature louse. In particular, FIG. 1A is a magnified view of a louse 100. Head lice are tiny, wingless parasitic insects that infest the hair and scalp of humans and can be very difficult to eliminate. They are roughly 2.5-3.5 mm measured along their longest dimension. Lice can be very hard to see, depending on the type of hair they inhabit, and unless there are many of them, due to the speed with which they can travel. It is reported that lice can travel up to 23 cm per minute.
Head lice develop in three stages: nits (lice eggs), nymphs (immature, non-laying adults), and louse (mature, laying adults). Lice eggs are generally reported to take from 7-14 days to hatch into nymphs. Nymphs mature into laying adults about 7-14 days after hatching. Adult lice begin laying eggs 0-2 days thereafter, and live approximately 4-5 weeks total. The louse life cycle appears to vary based on temperature, humidity, food supply, and other factors. Lice obtain nourishment by sucking blood from the scalp. Without access to blood, lice typically survive for 1-2 days, but under favorable conditions, can live up to 4 days.
FIG. 1B depicts a lice infestation in blond hair. More particularly, a number of nits are circled and indicated as 110a-110c. Nits 110a-110c appear to be relatively immature, based on their dark color, which changes from dark brown when they are laid, to light brown or tan as they near hatching, to white or translucent, once the egg sac is empty.
FIGS. 1C and 1D depict nits. Nits are eggs laid by an adult louse in an associated sac that is attached to a human hair. Nits are white when they are first laid, turn brown before they hatch, and are again yellowish-white once they are empty. FIG. 1C shows an egg sac with egg 120 and an empty egg sac 121. The egg sacs are glued firmly onto individual hairs, generally near the scalp, but can also be found 5 or more inches down an individual hair. Nits can survive for up to 10 days away from the scalp. Nits are approximately 0.5-1 mm in length (along the longest dimension) and oval in shape. FIG. 1D shows a nit 130 (circled for presentation) attached to a hair 132 and displayed with respect to a penny coin 131 to illustrate the small size of the nit 130.
Head lice are not, in and of themselves, dangerous, but they do create an intense nuisance and drain on parents', schools', and other's time, energy, finances, and patience, not to mention the discomfort and potential embarrassment experienced by the affected person. Approximately 60% of schools and childcare centers in the U.S. have adopted a “no nit” policy such as one recommended by the National Pediculosis Association (http://www.headlice.org/downloads/nonitpolicy.htm). Adoption of this policy means children cannot attend school if nits (lice eggs or egg sacs) are found in their hair.
No-nit policies are a controversial subject. The American Academy of Pediatrics, for example, has issued a position statement discouraging no-nit policies in schools (http://aappolicy.aappublications.org/cgi/content/full/pediatrics;126/2/392.) Excluding the time and attention given to lice infestations by school teachers and administrators, lice infestations are estimated to result in 12-24 million US dollars lost school days per year for the children along with 4-8 billion US dollars lost per year for missed workdays by parents who have to stay home with them.
It is not known how, exactly, lice are transmitted from one person to another. It is assumed that lice travel (e.g., walk, crawl) from one person to the next and that that this is the most common means of transmission. This does not appear to have been scientifically confirmed, however. Lice do not jump or fly. There appears to be general agreement that infestations are spread from person to person when a person having a lice infestation comes into close contact with someone without lice. Various modes of transmission have been proposed, but none appear to have been definitively confirmed. Transmission may occur, for example, when children play in close proximity of one another during classroom activities (e.g., at play, during group reading time); by sharing infested clothing (e.g., hats, scarves, coats or hair ties); by sharing an infested brush, comb or towel; by sharing a stuffed animal that has been contaminated (i.e., fomite transmission); or by laying their head down against an infested surface (e.g., a pillow or blanket).
Several epidemiological studies have shown no association between head lice and the sharing of combs, brushes, towels, scarves, hats, and/or clothes. The authors of another study concluded that classroom floors are also not instrumental in the transmission of head lice. The research does appear to show that lice, when they feel threatened, will move to the periphery of a hair, ready to drop off if the perceived danger warrants evacuation. This “flea response” appears to be a viable mode of transmission.
Lice can also survive submersion in water, such as in a swimming pool, bath or shower. However, when lice become immersed, they appear to go into statis and clasp firmly to the hair to which they were attached at the time of the immersion, refusing to leave their host. It has been shown that head lice can live up to 19 hours after being immersed in water.
Regardless of how a person acquires lice, getting rid of them is challenging. Some families experience ongoing infestations that last many months or even years. There are three general approaches taken to treat infestations, generally used in combination with one another: chemical treatment, non-toxic suffocation, and manual removal.
Numerous chemical formulations have been developed over the years to get rid of live lice using active ingredients such as: malathion (brand name: Ovide®), permethrin (brand names: NIX®, RID®, A-200®, Clear®), dimethicone (brand name: LiceMD), pyrethrum (brand names: RID, A-200, Clear, Pronto, R & C), phenothrin, lindane (brand name: Kwell®), oral trimethoprim-sulfamethoxazole, phenothrin, piperonyl butoxide, and various combinations thereof. These chemicals are generally intended to act on the central nervous system of lice but are inherently toxic to humans as well, which makes using them undesirable for many. The use of lindane, for example, is highly controversial. It is an organochloride with similar properties as DDT, and is known to cause neurotoxicity and anemia.
The toxicity of these formulations aside, these products may suffer from other problems as well. There have been numerous reports that lice are adapting to the chemicals and developing resistance, much like bacterial resistance to antibiotic use. In addition, the effectiveness of at least some of these products is in doubt. One percent lindane, for example, was shown to have killed only 17% of lice using the recommended application time. Moreover, most of these products only kill live lice—they do not kill live eggs, which will subsequently hatch and require additional treatment. Furthermore, as the chemical treatments continue to be used, resistance is expected to increase.
Alternatively, many people are interested in non-toxic and/or “traditional” methods used to kill lice by suffocating them, including approaches such as: coating hair in olive oil, petroleum jelly (e.g., Vaseline), coconut oil, castor oil, vegetable shortening (e.g., Crisco), and other oils with or without adding benzyl alcohol, herbal oils, essential oils (e.g., lavender, anise, tea tree oil). Commercially available suffocation products include products and compounds such as: Hair-Clean-1-2-3® (a combination of anise, coconut and ylang ylang oils in an alcohol base) and LiceRX (a combination of various oils, lavender, patchouli, camphor, geranium and others). It is thought that the essential oils and alcohol act by “shocking” the openings on the sides of lice that are used for breathing (spiracles), and keeping them open long enough to allow the oil to clog them, thus blocking the opening and leading to suffocation.
Regardless of the treatment used, “nit-picking”—manually finding and removing nits—is always necessary. Each egg sac is affixed to a hair with a glycoprotein glue that acts as an extremely strong cement that is highly resistant to removal. A thorough nit-picking of a head of medium-length hair usually takes from one to two hours to complete. It is generally recommended that nit-picking be performed in direct lighting, posing an added challenge in winter months before and after school hours when lighting is generally not very good. Seeing each and every nit can be virtually impossible in any lighting condition and many, if not most, nits are simply missed. Unfortunately, missing even one viable nit can result in a new round of infestation.
Typically, fine-toothed combs are used to remove nits from a patient's hair. However, such combs often fail to remove all or even a substantial percentage of nits. Moreover, such combs and other devices/systems for lice and nit removal do not help the caretaker effectively find nits in order to visually confirm an infestation diagnosis or assist in manually removing the nits. In one approach, a comb is used in conjunction with a magnifying glass. However, a magnifying glass may cause eye strain and in any event does not support efficient inspection of a large number of hairs. In another approach, product dyeing compound is used to dye nits a fluorescent color, thereby making them easier to see for subsequent removal. However, this technique may have drawbacks including stains, limited applicability to darker colored hair, and the like.